A solid state drive (SSD) is a data storage device that uses integrated circuit assemblies as memory to store data persistently. SSDs have no moving mechanical components and this distinguishes SSDs from traditional electromechanical magnetic disks, such as, hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read/write heads. Compared to electromechanical disks, SSDs are typically more resistant to physical shock, run silently, have lower access time, and less latency. Many types of SSDs use NAND-based flash memory which comprises an electronic (solid-state) non-volatile computer storage medium that can be electrically erased and reprogrammed.
NAND-based flash memory stores information (i.e., data) in individual memory cells. In single-level cell (SLC) NAND flash technology, each memory cell may exist in one of two voltage states, storing one bit of information per memory cell. A multi-level cell (MLC) is a memory cell capable of storing more than a single bit of information. For example, a MLC NAND flash memory that has sixteen possible voltage states per memory cell may store four bits of information per memory cell, and may be referred to as a quad-level cell (QLC) NAND.